The present invention relates to a developing device and an electric energy supply part for applying a developing bias to a developer carrying member.
In a congressional apparatus for forming a multi-color image through an electrophotographic image formation process, a plurality of developing devices accommodating developers having different colors are provided on a rotary selecting mechanism; an electrophotographic photosensitive member(photosensitive drum) is electrically charged uniformly by a charging device and is selectively exposed to light so that electrostatic latent image is formed; and the selecting mechanism is operated so as to choose a developing roller as a developer carrying member (developing means) of a developing device accommodating a predetermined color developer (toner) to the photosensitive drum. The developing roller is rotated while being supplied with a developing bias so that electrostatic latent image on the photosensitive drum is developed into a toner image. The toner image is transferred onto a recording material, and the developing and transferring operations are repeated for the respective colors, thus providing a multi-color image.
Recently, a process cartridge containing as a unit process means such as the photosensitive drum, the developing means actable on the photosensitive drum, the charging means, cleaning means or the like has been made available.
As for a developing device or process cartridge, a proposal for a structure of an electric power supply contact of a developing bias to a developing roller (developing means) has been made wherein a flange member of an electroconductive member is provided at an end of a developing roller; an electrode in the form of a compression coil spring is mounted to the flange member for electrical conduction; an end of the compression coil spring is contacted to a contact member which is mounted to a housing of the developing device and which is electrically conducted to the electric energy supply member provided in the main assembly of the apparatus when the developing device is mounted to the main assembly of the apparatus.
As another structure of the electric power supply contact for the developing bias to the developing roller (developing means), an elastic contact portion is provided in the contact member, and the elastic contact portion is contacted to the flange member of an electroconductive member provided a an end of the developing roller.
In the case of the electric power supply contact structure, the compression coil spring is rotated integrally with the developing roller, and slides relative to the coil spring, and therefore, in general, grease is applied to the sliding portion. In the latter case of the electric power supply contact structure, the flange member is rotated integrally with the developing roller, and slides relative to the elastic contact member, and therefore, in general, electroconductive grease is applied to the sliding portion.
In addition, in the latter electric power supply contact structure, in order to stabilize the contact pressure of the sliding contact portion to the flange member of the elastic contact member, the spring constant of the elastic contact member is desirably minimized to make the degree of deformation larger. In such a case, a space is required to assure the deformation of the elastic contact member between the developing roller and the supporting frame supporting the developing roller in the developing device or the process cartridge.
The present invention is concerned with a further development of the prior-art, and it is a principal object of the present invention to provide a developing device in which a space applied by the electric power supply contact mechanism for the developer carrying member is reduced with the improved reliability of the contact portion of the electric power supply contact.
It is another object of the present invention to provide an electric energy supply part for supplying electric energy (developing bias voltage) to the developer carrying member with contact electric power supply contact for supplying electric power to the developing roller.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.